Lubricating oil and lubrication therewith



Patented Nov. 5, 1940 UNITED STATES PATENT OFFICE THEREWITH Arthur Walther Lewis, Elizabeth, N. J.-, assignor to Tide Water Associated Oil Company, Bayonne, N. 1., a corporation ofDclaware No Drawing. Application March 12, 1937, Serial No. 130,513

7 Claims.

This invention relates to lubricants intended for service in the lubrication of internal combustion engines. The invention more particularly is concerned with lubricating or motor oils of mineral hydrocarbon origin which are normally corrosive toward bearing metal alloys of the character of cadmium-silver, cadmium-nickel, or copper-lead; and has, for an important objective, the inhibition or prevention of deterioration of 10 such bearing metal in service by the corrosive action of the lubricant thereon.

Engine bearings comprising or surfacedwith cadmium-silver or like alloys now are frequently employed in lieu of the more usual Babbitt metal bearings, in order to cope with extreme service conditions of friction and temperature. These conditions are the consequences of moderndevelopments in internal combustion engines making available high sustained speeds and requiring bearings formed of metals or alloys having great er resistance to wear, and further characterized by higher melting points necessary to prolonged life under the extreme thermal conditions existing during operation of the engine. Temperatures at the bearing surfaces during operation are much higher in the case of engines requiring these new bearings than formerly was the circumstance with engines in which Babbitt metal bearings gave satisfactory service.

Experience with bearings of the character or type exemplified by cadmium-silver, cadmiumnickel and copper-lead alloys has demonstrated,

however, that their utility is greatly impaired by an extreme susceptibility to rapid deteriora- 85 tion by the corrosive action or effect of many available lubricating oils. Particularly has this effect been noted when the oils are of the character generally regarded as superior lubricants by conventional criteria.

Little is known concerning the nature of the corrosive action or its causes; but in general it has been observed that motor oils derived from selected crudes predominantly paraflinic in origin, as well as those oils from these or other crudes which have been improved by treatment with selective solvents, exhibit a marked tendency toward corrosion of the hearings in question, although by other tokens the lubricant is of superior quality. Oxidation stability, as indicated by sludge or acid formation in conventional tests indicative of the tendency toward deterioration of the oil itself in service, does not appear to have reliable correlation with the tendency of the oil to corrode bearing surfaces. It is possible that the high bearing surface temperatures existing under service conditions with the new bearings may be a factor in occasioning the observed deleterious efiect of motor oils thereupon. It would appear, also, that the problem of bearing corrosion, with which the present invention is par- 5 ,ticularly concerned, contrasts with problems of lubricant deterioration per se, since oils characterized by long life and good stability may be just as corrosive as those of inferior grade. No theory in explanation of the observed corrosivelO action or the prevention thereof, as herein proposed according to the invention, is intended to be relied upon.

According to the present invention, it has now been found that the corrosive effect of lubricat- 15 ing oils upon bearing surfaces of the character referred to above may be avoided in novel and effective manner by incorporating with such oils particular compounds having a retarding or inhibiting effect in respect of such corrosion. More 20 specifically, the invention arises from the discovery that a compound comprising a di-amino diphenylamine effects a very beneficial retardation of the corrosive action of internal combustion engine lubricating oils upon cadmium-silver, cad- 25 mium-nickel, copper-lead and like bearing metal alloys.

It is, therefore, an important object of the present invention to inhibit or retard the corrosive deterioration of cadmium-silver and like bear-.30 ing metal alloys in automotive service by providing a lubricant therefor comprising a refined mineral hydrocarbon oil having incorporated therewith a di-amino diphenylamine in small but effective proportion. Likewise, it is an object of the invention to improve, and to prepare improved, motor oils of petroleum origin by incorporating therein a di-aminodiphenylamine in corrosion inhibiting proportions. The provision of an inhibitor effective for such purpose and comprising the aforementioned compound naturally is a major objective.

Viewed in another aspect, the invention may be regarded as encompassing a novel method of lubricating bearing metal surfaces, of the character of cadmium-silver, cadmium-nickel, copper-lead or like alloys, by applying thereto a film of lubricant comprising mineral hydrocarbon 'oil having incorporated therewith a small but effective proportion of a di-amino diphenylamine. With this method of lubrication it has been found that prolonged life and consequent improved service may be attained in the use of these alloys as bearing metals for internal combustion engines, particularly when operating conditions such as high sustained speeds under load occasion unusually high bearing surface temperatures. Ordinarily, the oil selected for use, in applying the lubricating method of the invention to its intended service, will be of a character generally regarded as of superior grade and refining. Thus, the invention finds particular utility in making possible the beneficial use of such oils by avoiding deleterious consequences otherwise encountered when no preventive measures are taken against the corrosive deterioration of bearing metal alloys as hereinbefore referred to. It will be understood, however, that the invention contemplates no limitation in this respect, and that the method oflubrication herein described may be practiced in conjunction with mineral hydrocarbon lubricating oils taken as a broad class and regardless of origin.

Solubility of a di-amino diphenylamine in mineral hydrocarbon oil of motor lubricating oil character is limited, but the proportion necessary to accomplish the objects of the present invention is well within the limits of solubility. It sufiices, therefore, simply to dissolve a di-amino diphenylamine (if desired with moderate application of heat to facilitate solution) in motor oil intended for service in internal combustion engines in order to prepare for the lubrication thereof according to the invention. Proportions of less than 0.2% by weight of the inhibitor dissolved in motor oil are shown hereinafter to be inhibitive of the corrosion normally attending the use of many lubricating oils with bearing metals of the type comprising cadmium-silver and like alloys. The stated percentage is not intended as a limitation upon the contemplated scope and practice of the invention, as obviously the inhibitor may be, and is intended to be, employed in any corrosion inhibiting proportion.

The tendency of motor oils to corrode bearings of the character in question may be determined by a convenient test which affords a ready method of obtaining a comparative evaluation of motor oils in the laboratory. In this test method a group of bearings, ordinarily including at least one each of several of the newer bearing metal alloys (viz: cadmium-silver, cadmium-nickel and copper-lead) is supported in a chamber in which air may circulate and the bearing surfaces are exposed for a period of 22 hours to a stream of oil sprayed under pressure continuously upon the corrodible area. The oil is maintained at a temperature of approximately 335 F. and the spray is so directed as to disperse the oil over the surfaces of the bearings. Means are provided for re-circulating the sprayed oil so that a given quantity is used for a given test thussimulating service conditions in'an engine. The measure of corrosion is taken as the loss in weight of the bearing per unit of exposed corrodible surface.

The test method-described above is carried out in the familiar Underwood corrosion apparatus supplied by the Scientific Instrument Company of Detroit, Michigan, in accordance with General Motors specifications.

Results obtained utilizing the foregoing test for comparative evaluation of motor oils with and without an inhibitor according to the invention provide specific illustration of the value and inhibiting effectiveness of a di-amino diphenylamine. The oil used for the test was an S. A. E. 20 motor oil comprising a blend of solvent refined Pennsylvania neutral oil with a conventionally produced Pennsylvania bright stock and having an A. P. I. gravity of 30.1, Saybolt viscosity at 100 F. of about 300 seconds, Saybolt viscosity at 210 F. of 54 seconds and flash point of 425 F. In view of the limited solubility of diamino diphenylamine in motor oils, a saturated solution was prepared by stirring into one portion of the oil an amount of 2,4 di-amino diphenylamine equivalent to 0.2% by weight based on the oil, permitting the excess to settle and draining on a saturated solution. The oilwas warmed to facilitate dissolving the compound therein. During each run cadmium-silver, cadmium-nickel and copper-lead bearings all were present; and comparative losses in weight per square decimeter due to corrosion were observed as follows for the The above illustrative example clearly demonstrates the eflicacy of a di-amino diphenylamine in occasioning effective retardation of bearing corrosion normally resulting from the use of internal combustion engine motor oil with bearings of the type described. Tests on the used oil followingeach of the foregoing runs evidenced the further utility of inhibitors according to the invention in reducing deterioration of the oil itself. Thus, used oil from the run in which no inhibitor was present was found to have undergone an increase in carbon residue from about 0.4 to 2.10. The neutralization number of the used oil from the blank run was 4.25 milligrams KOH per gram of oil.

Comparative tests on the used oil after the reported run in which a di-amino diphenylamine was present showed an increase in carbon residue from about 0.4 to 0.96, and a neutralization number of 1.12 milligrams KOH per gram of oil. The

The tests were run in an eight cylinder automobile engine equipped with connecting-rod bearings of the newer type exemplified by the alloys mentioned above; and operated under carefully controlled conditions duplicated in successive runs with and without inhibitor present in the lubricating oil. New bearings carefully weighed were used for each run, and each set comprised alternate cadmium-silver and copper-lead bearings respectively. Operating conditions included an engine speed of 2850 R. P. M. under a load of 50 brake horsepower and a running period of 15 hours, this being the equivalent of 768 miles travel at a speed of 51.2 miles per hour. Crankcase oil temperature was maintained at 300 F. and water temperature at 200 F. The oil consequently was subjected to lubricating service far more severe than that normally to be encountered in ordinary automotive use. At the end of each run the bearings were removed and again weighed, the loss in weight giving a measure of corrosion caused by the lubricant.

Tested in an engine under the foregoing conditions an S. A. E. 20 motor oil, of the character and specifications used in the laboratory evaluations reported earlier herein, gave the following results:

The evidence presented by all the foregoing data clearly shows the operative significance of a di-amino diphenylamine as a valuable addition to motor oils intended for service in the lubrication of engines equipped with cadmium-silver and like alloy bearings. For many circumstances of normal automotive use it is likely that even greater benefit than that indicated by the foregoing engine test of accentuated se erity will result since operating conditions ordinarily encountered are not as stringent as those of the test reported herein.

While the utility of the invention has been illustrated specifically with reference to a particular motor oil, no limitation is to be inferred therefrom, and other oils, whether or not comparable in specification or origin,rmay be used in the lubrication of bearings of the type described in accordance with the invention.

I'claim:

1. The method of lubricating bearings having substantially the corrosion susceptibility characterizing cadmium-silver, cadmium-nickel and copper-lead alloys, which consists in applying to the bearing surfaces lubricant comprising mineral hydrocarbon oil of a character normally tending to corrode said alloys and having incorporated therein corrosion inhibiting proportions of a di-amino diphenylamine.

2. The method of lubricating bearings having substantially the corrosion susceptibility characterizing cadmium-silver, cadmium-nickel and copper-lead alloys, which consists in applying to the bearing surfaces lubricant comprising mineral hydrocarbon oil of a character normally tending to corrode said alloys and having incorporated therein corrosion inhibiting proportions of 2,4 di-amino diphenylamine.

3. The method of lubricating bearing surfaces in internal combustion engines, which bearing surfaces comprise an alloy having substantially the corrosion susceptibility characterizing cadmium-silver, cadmium-nickel, and copper-lead 5 alloys, which consists in applying to said bearing surfaces lubricant comprising mineral hydrocarbon oil of a character normally tending to corrode said alloys and having incorporated therein corrosion inhibiting proportions of a di-amino diphenylamine.

4. The method of lubricating bearing surfaces in internal combustion engines, which bearing surfaces comprise an alloy having substantially the corrosion susceptibility characterizing cadmium-silver, cadmium-nickel, and copper-lead alloys, which consists in applying to said. bearing surfaces lubricant comprising mineral hydrocarbon oil of a character normally tending to corrode said alloys and having incorporated therein corrosion inhibiting proportions of 2,4 di-amino diphenylamine.

5. In the lubrication of bearing surfaces, at least one of which is formed of an alloy having substantially the corrosion susceptibility characterizing cadmium-silver, cadmium-nickel and copper-lead alloys, with mineral hydrocarbon oil normally tending to cause substantial and rapid corrosion thereof, the method'of inhibiting such corrosion, which comprises incorporating with said oil corrosion inhibiting proportions of a diamino diphenylamine.

6. In the lubrication of bearing surfaces, at least one of which is formed of an alloy having substantially the corrosion susceptibility characterizing cadmium-silver, cadmium-nickel and copper-lead alloys, with mineral hydrocarbon oil normally tending to cause substantial and rapid corrosion thereof, the method of inhibiting such corrosion, which comprises incorporating with said oil corrosion inhibiting proportions of 2,4 diamino diphenylamine.

'7. The method of claim 5, further characterized in that said di-amino diphenylamine is incorporated with said oil in proportion sufficient to 5 form a saturated solution.

AR'I'HUR WALTHER LEWIS. 

